Your 4runner will do just fine, in fact it will probably surprise you just how well it appears to take on what may seem like challenging terrain to you.
First time I ever went wheeling i was pretty nervous and stopped and poked a stick into every puddle on the track to see how deep it was, but after many years of experience i often find myself accellerating into them now! (Dont do that, its bad for the environment and your car)
Read the 'sticky' article on off roading tips at the top of this sub-forum. It is very good and will help you alot.
Have fun!